This invention relates to a aggregate/binder rotating mixing drum with a replaceable liner, and particularly to such a mixing drum for mixing an aggregate with a plastic binder.
Mixing drums are used for mixing of various materials to form a substantially uniform mixture of the several different materials or ingredients. Metal mixing drums are widely used in many applications because of the improved wear characteristics. Typically, in concrete and other similar binder and aggregate based mixing systems, various metal drums have been designed and are widely used for intermixing of the cement, aggregate and other materials to form a final product such as concrete and the like. With the development of plastic binders, various products have been developed involving the inter-mixing of aggregate material and a plastic binder material. A particular product which has been developed includes an epoxy resin binder which is intermixed with decorative aggregate to form a decorative material which is applied as a final decorative surface. The decorative material is generally applied as a decorative top layer overlying a concrete and other similar underlayments for patios, driveways and the like. The decorative material has been generally mixed in a conventional rotating mortar mixing drum having internal agitating and paddle units to insure thorough mixing, similar to the system used for many years for mixing cement and concrete. The mixing drum must be cleaned after each use to prevent build up and accumulation of product within the drum and thereby insure that subsequent mixtures are thoroughly intermixed and are not contaminated by the previous mixture. Cleaning can be particularly difficult when handling plastic binders such as epoxy resins.
Various mixing devices have been available with a liner removably secured to the drum for rotation with the drum, with a removable liner for easy cleaning after use of the mixing apparatus. U.S. Pat. No. 4,521,116 discloses a rotating drum apparatus in which a cylindrical drum is provided. A special plastic liner is bolted within the drum and includes a complementing cylindrical portion which telescopes into the drum and substantially conforms to the drum. The liner is bolted to the drum and rotates therewith. The liner includes an outer cone-shaped portion which is integrally formed with the cylindrical portion and which is specially constructed for positioning outwardly of the drum. The bolted liner can be released and removed for cleaning of epoxy mixture residue within the liner.
Although the liner promotes easy cleaning, the present inventor has found that epoxy resin aggregate mixing and the like presents certain problems with respect to the thoroughness of the mixing and the conventional construction of the liner and develops pockets within the system which interfere with the thorough mixing of the product and may result in undesirable agglomeration of residue within liner pockets which are difficult to clean thoroughly. Further, the projecting liner can raise certain questions with respect to the stability of the system, the required construction of the liner to withstand the forces encountered in loading and operating the lined mixer and the like.